New OEM gas tank for 66 valiant but want 1/2 lines to carb?

The guys are right 3/8" will be big enough for your application. But to answer you question AN 8 is 1/2" size. AN fittings are in 16ths of an inch: AN 4 = 4/16 or 1/4", AN 6 = 6/16 or 3/8", AN 8 = 8/16 or 1/2", AN 10 = 10/16 or 5/8", AN 12 = 12/16 or 3/4", AN 14 = 14/16 or 7/8" and AN 16 = 16/16 or 1"